Reactivity of transition elements decreases almost regularly from Sc to Cu because of

Options

A. lanthanoid contraction
B. regular increase in ionisation enthalpy
C. regular decrease in ionisation enthalpy
D. increase in number of oxidation states.

Answer

To solve the question regarding the reactivity of transition elements decreasing from Scandium (Sc) to Copper (Cu), we can break down the reasoning into several steps:

### Step-by-Step Solution:

1. **Understanding Reactivity in Transition Elements**:
- Reactivity of transition metals is often related to their ability to lose electrons and form positive ions. The easier it is to remove an electron, the more reactive the element is.

2. **Ionization Enthalpy**:
- Ionization enthalpy is defined as the amount of energy required to remove the most loosely bound electron from an atom in the gaseous state. As we move across a period from left to right, the ionization enthalpy generally increases.

3. **Trend from Sc to Cu**:
- As we move from Scandium (Sc) to Copper (Cu), we observe that the atomic number increases, leading to an increase in the nuclear charge. This increase in nuclear charge results in a stronger attraction between the nucleus and the electrons, making it more difficult to remove an electron.

4. **Inversely Proportional Relationship**:
- Since reactivity is inversely proportional to ionization enthalpy, as the ionization enthalpy increases, the reactivity of the transition elements decreases.

5. **Conclusion**:
- Therefore, the reactivity of transition elements decreases almost regularly from Sc to Cu primarily due to the regular increase in ionization enthalpy.

### Final Answer:
The reactivity of transition elements decreases almost regularly from Sc to Cu because of the regular increase in the ionization enthalpy.

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